In this article, we will learn about the Android Platform Architecture which supports different mobile device needs. We will discuss about Android Platform Architecture components one by one.
Android is an open source, Linux-based software stack created for a wide array of devices and form factors. The following diagram shows the major components of the Android platform.
Android software stack contains a Linux Kernel, HAL, collection of c/c++ libraries which are exposed through an application framework services, runtime, and application.
In these components, the Linux Kernel is the main component in android to provide its operating system functions to mobile and Dalvik Virtual Machine (DVM) which is responsible for running a mobile application.
Following are main components of android architecture those are :
- Linux Kernel
- Hardware Abstraction Layer(HAL)
- Native C/C++ Libraries
- Android Runtime
- Java API Framework
- System Apps
1. Linux Kernel
The foundation of the Android platform is the Linux kernel. For example, the Android Runtime (ART) relies on the Linux kernel for underlying functionalities such as threading and low-level memory management.
Using a Linux kernel allows Android to take advantage of key security features and allows device manufacturers to develop hardware drivers for a well-known kernel.
Linux Kernel is a bottom layer and heart of the android architecture. It manages all the drivers such as display drivers, camera drivers, Bluetooth drivers, audio drivers, memory drivers, etc. which are mainly required for the android device during the runtime.
The Linux Kernel will provide an abstraction layer between the device hardware and the remainder of the stack. It is responsible for memory management, power management, device management, resource access, etc.
2. Hardware Abstraction Layer (HAL)
The hardware abstraction layer (HAL) provides standard interfaces that expose device hardware capabilities to the higher-level Java API framework.
The HAL consists of multiple library modules, each of which implements an interface for a specific type of hardware component, such as the camera or bluetooth module. When a framework API makes a call to access device hardware, the Android system loads the library module for that hardware component.
3. Native C/C++ Libraries
Many core Android system components and services, such as ART and HAL, are built from native code that require native libraries written in C and C++. The Android platform provides Java framework APIs to expose the functionality of some of these native libraries to apps. For example, you can access OpenGL ES through the Android framework’s Java OpenGL API to add support for drawing and manipulating 2D and 3D graphics in your app.
If you are developing an app that requires C or C++ code, you can use the Android NDK to access some of these native platform libraries directly from your native code.
The following are the summary details of some core android libraries available for android development:
- Media library for playing and recording audio and video formats
- The Surface manager library to provide a display management
- SGL and OpenGL Graphics libraries for 2D and 3D graphics
- SQLite is for database support and FreeType for font support
- Web-Kit for web browser support and SSL for Internet security.
4. Android Runtime
For devices running Android version 5.0 (API level 21) or higher, each app runs in its own process and with its own instance of the
Android Runtime (ART).
ART is written to run multiple virtual machines on low-memory devices by executing DEX files, a bytecode format designed specially for Android that’s optimized for minimal memory footprint. Build toolchains, such as
Jack, compile Java sources into DEX bytecode, which can run on the Android platform.
Some of the major features of ART include the following:
- Ahead-of-time (AOT) and just-in-time (JIT) compilation
- Optimized garbage collection (GC)
- On Android 9 (API level 28) and higher, conversion of an app package’s Dalvik Executable format (DEX) files to more compact machine code.
- Better debugging support, including a dedicated sampling profiler, detailed diagnostic exceptions and crash reporting, and the ability to set watchpoints to monitor specific fields.
Prior to Android version 5.0 (API level 21), Dalvik was the Android runtime. If your app runs well on ART, then it should work on Dalvik as well, but the reverse may not be true.
Android also includes a set of core runtime libraries that provide most of the functionality of the Java programming language, including some Java 8 language features, that the Java API framework uses.
5. Java API Framework
The entire feature-set of the Android OS is available to you through APIs written in the Java language. These APIs form the building blocks you need to create Android apps by simplifying the reuse of core, modular system components and services, which include the following:
- A rich and extensible View System you can use to build an app’s UI, including lists, grids, text boxes, buttons, and even an embeddable web browser
- A Resource Manager, providing access to non-code resources such as localized strings, graphics, and layout files
- A Notification Manager that enables all apps to display custom alerts in the status bar
- An Activity Manager that manages the lifecycle of apps and provides a common navigation back stack
- Content Providers that enable apps to access data from other apps, such as the Contacts app, or to share their own data.
Developers have full access to the same framework APIs that Android system apps use. The application framework includes services like telephony service, location services, notification manager, NFC service, view system, etc. which we can use for application development as per our requirements.
6. System Apps
The top layer of the android architecture is System Applications. The native and third-party applications like contacts, email, music, gallery, clock, games, etc. whatever we will build those will be installed on this layer only.
The application layer runs within the Android run time using the classes and services made available from the application framework.
The system apps function both as apps for users and to provide key capabilities that developers can access from their own app. For example, if your app would like to deliver an SMS message, you don’t need to build that functionality yourself—you can instead invoke whichever SMS app is already installed to deliver a message to the recipient you specify.
Thanks for reading ! I hope you enjoyed and learned about the Android Platform Architecture Components. Reading is one thing, but the only way to master it is to do it yourself.
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